Circuit for regulating the mean frequency of an oscillating system

ABSTRACT

A circuit for regulating the mean frequency of an oscillating system by temporarily connecting a capacity to said oscillating system by means of an electronic switch controlled by a phasedetecting system to which are applied the frequency of said oscillating system and a reference frequency.

United States Patent Berney [451 July 4,1972

[54] CIRCUIT FOR REGULATING THE MEAN FREQUENCY OF AN OSCILLATING SYSTEM[72] lnventor: Jean Claude Berney, Lausanne, Switzerland [73] Assignee:Compagnie des Montres Longines, Francillon S.A., Bern, Switzerland [22]Filed: May 5, 1970 211 App]. No.: 34,733

[30] Foreign Application Priority Data May 8, 1969 Switzerland ..7066/69[52] U.S.Cl ..331/8,33l/14,331/27, 331/36 C, 331/117 R, 331/177 R,331/179 [51] Int. Cl. ..1-103h 3/04 [58] Field ofSearch ..331/8, 14,27,36 R, 36 C, 331/177 R,179, 117 R [56] References Cited UNITED STATESPATENTS 3,076,154 1/1963 Rappold et a1 ..33 1/177 3,080,533 3/1963Edwards ...331/27 X McCoy ..332/29 Hepner ..331/34 X PrimaryExaminer-Roy Lake Assistant ExaminerSiegfried 1-1. Grimm Atlomeylmirie &Smiley [57] ABSTRACT A circuit for regulating the mean frequency of anoscillating system by temporarily connecting a capacity to saidoscillating system by means of an electronic switch controlled by aphasedetecting system to which are applied the frequency of saidoscillating system and a reference frequency.

2 Claims, 1 Drawing Figure Patented July 4, 1972 3,675,147

C11 T1 T2 Rflfl Ru R l R2 INVENTOR.

JEAN g. 8ERNE'Y Attvs.

CIRCUIT FOR REGULATING THE MEAN FREQUENCY OF AN OSCILLATING SYSTEM Thisinvention relates to a circuit for regulating the mean frequency of anoscillating system to a value f fo/n, f being a reference frequency.Such a circuit may preferably be used as a frequency divider, forinstance in a quartz clock or watch wherein a stable high frequency hasto be divided for driving the wheels of a watch or counter. Priorfrequency dividers used for this purpose comprise for instance binarydividing stages and therefore such frequency dividers are complicatedand cumbrous and have high energy consumption.

This invention aims in avoiding said disadvantages of prior systems byproviding a circuit wherein a capacity causing shifting of said naturalfrequency by Af f/2n when connected to said oscillating system isadapted to be connected to this oscillating system by means of anelectronic switch controlled for being alternatively fully opened orclosed by an onoff detecting system for bringing back said meanfrequency of the oscillating system to f. With this relatively simplesystem it is possible to bring back the mean frequency of an oscillatingsystem of limited stability to an accurate value in a fixed ratio to asubstantially higher stable reference frequency. In this way relativelyhigh division ratios per stage may be obtained such that a small numberof dividing stages are needed for obtaining very high and stabledividing ratios. The stability of each stage is particularly high due tothe on off control of the electronic switch and of the frequency,shifting capacity respectively, as compared with the stability of anysystem with analogous control.

One embodiment of this invention will now be explained in detail and byway of example with reference to the accompanying drawing.

The oscillating system of this embodiment is constituted by anoscillating circuit LC of which the oscillation is sustained in a mannerwell known in the art and not shown. A capacity C of a suitable valuemay be connected in parallel with the capacity C of the oscillatingcircuit by means of an electronic bidirectional switch formed bytransistors T, and T By means of a condenser C the sinusoidaloscillation of the oscillating circuit LC is transmitted to the base ofa transistor T biased through resistor R Transistor T is a class Camplifier for the signal of the oscillating circuit such that apractically rectangular signal appears at the load resistor R Thisrectangular signal is difierenciated by a condenser C and a resistor Rand then amplified by a transistor T This transistor fonns an AND gatetogether with a transistor T this gate serving as a phase detector.Transistor T is controlled through a resistor R,, by a rectangularsignal at a reference frequency or pilot frequency f0. Transistors T,and T are series'connected with a memory circuit formed by a condenser Cand two biasing resistors R and R connected in series. The tap pointbetween resistors R and R is connected to the base of a transistor Tthis transistor controlling the electronic switch T,, T, through tworesistors R, and to.

The natural resonance frequency of circuit LC is tuned to a valuecomprised between f and f Af. In other language, the natural frequencyof circuit LC is slightly higher than the nominal frequency fo/n.However, the frequency of the oscillating circuit may be suflicientlycorrected for bringing its mean frequency back to the value f fo/n whencapacity C, is connected in parallel with the capacity C of theoscillating circuit. To this end the value of the capacity C should beselected in such a manner that it causes a frequency shifi Af== fl2nwhich is suficient but not too high. For the value Af given above thevalue of C, is approximatively equal to C/n.

Control of the bidirectional switch T,, T, is efiected by the phasedetector T T When the pulse amplified by T arrives during the period ofconduction of T that is when transistors T, and T, are conducting at thesame time, condenser C is charged. The time constant of C,, R and R, isso selected that '1, remains conducting during a full period of theoscillating circuit LC. When transistor T is conducting transistors T,and T, of the electronic switch are also conducting, that is, capacit Cis connected in allel with ca acit C for reducin the ti' eqiiency of theoscill ing circuit L to a value f A 8 fa f- When during the next periodthe pulse amplified by transistor T, does no longer arrive at the sametime as a pulse of the input signal fo, transistor T a and consequentlytransistors T, and T, remain cut ofl" and the frequency of theoscillating circuit LC increases to the level of f +Af until anothercorrection is made when transistors T, and T, are conducting at the sametime. The mean frequency of the oscillating system is thus maintained ata value of f fo/n.

lf Af, is the deviation of the natural frequency of the oscillatingsystem (0 AfR Af) n is the number of periods during which the switch isopen n,is the number of periods during which the switch is closed then"1 fn M) "Afr A complementary circuit might be provided wherein theelectronic switch is opened instead of being closed for correction whenthe phase detector indicates coincidence of the pulses for cutting outthe capacity C, in order to increase the natural frequency of theoscillating system, this natural frequency being slightly below thenominal mean value of fo/n when capacity C, is connected to theoscillating system. The oscillating system may also include a mechanicalresonator, such as a tuning fork: or the like to which the capacity Cmay be connected for correction of the frequency through anelectromechanical transducer.

What is claimed is:

l. A circuit for regulating the mean frequency of an oscillating systemto a value f fo/n, fo being a reference frequency and n being a ratioexceeding 1, wherein the natural frequency of said oscillating system iscomprised between f and f A f, and wherein a capacity causing shiftingof said natural frequency by A f fl2n whereby it is equal to said ration, is adapted to be connected to said oscillating system by means of anelectronic switch controlled for being alternatively fully opened orclosed by an on-ofi" phase detecting system adapted to operate atdifierent input frequencies and having inputs for said referencefrequency f0 and the frequency of said oscillating system, saiddetecting system comprising a phase detecting, AND-gate controlled bysubstantially rectangular pulses at the reference frequency f0 and atthe frequency of the oscillating system, a memory circuit beingconnected between said detecting system and said elecuonic switch, saidmemory circuit maintaining said switch in open or closed condition inaccordance with the last information received from the output of saiddetecting system, said memory having a condenser in parallel with twoseries connected biasing resistors, the tap between said resistors beingconnected to the base of a control transistor for the electronic switch.

2 A circuit according to claim 1, wherein said AND gate includestransistors, said condenser of the memory circuit being series connectedwith said transistors of the AND-gate.

1. A circuit for regulating the mean frequency of an oscillating systemto a value f fo/n, fo being a reference frequency and n being a ratioexceeding 1, wherein the natural frequency of said oscillating system iscomprised between f and f + Delta f, and wherein a capacity causingshifting of said natural frequency by Delta f < OR = -f/2n whereby n isequal to said ratio n, is adApted to be connected to said oscillatingsystem by means of an electronic switch controlled for beingalternatively fully opened or closed by an on-off phase detecting systemadapted to operate at different input frequencies and having inputs forsaid reference frequency fo and the frequency of said oscillatingsystem, said detecting system comprising a phase detecting, ANDgatecontrolled by substantially rectangular pulses at the referencefrequency fo and at the frequency of the oscillating system, a memorycircuit being connected between said detecting system and saidelectronic switch, said memory circuit maintaining said switch in openor closed condition in accordance with the last information receivedfrom the output of said detecting system, said memory having a condenserin parallel with two series - connected biasing resistors, the tapbetween said resistors being connected to the base of a controltransistor for the electronic switch. CM,2Cuit according to claim 1,wherein said AND gate includes transistors, said condenser of the memorycircuit being series connected with said transistors of the AND-gate.